Hi Bogert! Ah, if it were only that simple! There are a number of 
reference sources (Klein Wassink, AWS Soldering Handbook, etc.) which 
contain the Arrehenius equation to calculate the oxide thickness over time 
for a given temperature. Unfortunately, you also need the diffusion 
coefficients and activation energies for the specific surface finish of 
concern (i.e. 100% Sn, 97/3 SnPb, 60/40 SnPb, etc.).  You also have a 
confounding/competing issue with the growth of intermetallic phase 
thickness occurring at the same time.  You can calculate an first order 
approximation on how fast a solderable surface finish will be consumed by 
the two reactions but each case is going to require a knowledge of your 
initial thicknesses. Components which require significant burn-in testing 
typically have fairly thick surface finishes. Any temperature over 100C 
results in a minimum tin oxide thickness of 10nm in a short period of 
time. Good luck.

Dave Hillman
Rockwell Collins
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Subject
[TN] Seeking Test Data on Oxidation of Pure Tin Component Leads Vs 
Temperature






March 8, 2008

Does anyone have test data that shows the degree of oxidation that may 
occur 
on pure-tin (<3% Pb) plated copper or other base metal component leads, 
when 
the components are subjected to electrical burn-in testing for 96 hours at 

125C, 150C, 175C (similar to the MIL-PRF-19500, Appendix E screening 
test)? 
What is a safe temperature for electrical screening testing that will not 
cause the components to fail J-STD solderability test?

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